Nowadays, reduced power consumption is required in all electrical devices. Pressures to reduce electrical consumption come from both consumers and public officials. The electrical consumption of a modern electronic device can be reduced by automatically switching off those parts of the device that are not necessarily required at that precise moment. If the device is in sleep mode consuming the least possible electrical power, all other parts of the device can be switched off, except for those sensing the arrival of a signal. When a signal arrives, and it is then wished for the device to operate, this sensing component activates the other parts of the device for normal operation. Such monitoring is typically implemented using a microcontroller in a special state consuming very little power, so that a part of the electronics is required that continuously takes sufficient, but as little as possible, power, by means of which the recognition of an input signal is sent to the microcontroller controlling the system.
In the case of loudspeakers, it is increasingly common for the loudspeaker itself to contain an amplifier, which achieves advantages especially in sound quality. Additional advantages are achieved, if the signal arriving at the loudspeaker is directly digitalized, whereby the signal between the loudspeaker and the sound source, which can be a preamplifier or a direct digital sound source, will be digital and thus in practice completely distortion-free.
Methods are known, by means of which in the aforementioned situation the loudspeaker's amplifier can be put into an energy-saving sleep mode by monitoring the digital signal arriving at the loudspeaker. According to the prior art, monitoring takes place in a decoder, on the basis of the analysis of which the subsequent loudspeaker stages are controlled. However, the microcircuit implementing the decoder takes a relatively large amount of energy even when in sleep mode, compared to the continuously tightening requirements.
More specifically, in the aforementioned technique, the digital (AES/EBU coded) audio-signal receiver is typically implemented as a microcircuit or module in a wider system circuit. In its normal operating state, the microcircuit implementing the decoder requires a current of 10-30 mA (30-100 mW). When the receiver is operating, it detects the arrival of a valid digital audio signal and can notify the rest of the system when a good digital signal can be received.
The power consumption of a device can be reduced by switching off the functions not being used. If a digital audio signal is not available, the circuit receiving a digital audio signal can be kept in a sleep mode consuming little power.